Preparation of transition metal ion modified bimetallic MXene and electrocatalytic application thereof

Abstract

This invention discloses a method for preparing bimetallic MXene modified by transition metal ions, which prepares different metal ions (Co) through electrostatic interactions. 2+ Ni 2+ and Mn 2+ ) and Mo2TiC2T intercalated with different concentrations x Material (labeled as Mo2TiC2T) x The study investigated the feasibility of modifying MXene materials by performing detailed characterization and analysis on the prepared samples. Analysis of the phase and morphology of the prepared samples revealed that transition metal ion intercalation of Mo2TiC2T... x The structure becomes more porous, significantly increasing its interlayer spacing. The introduction of metal ions can form new metallic bonds, facilitating efficient electron transfer. Electrochemical performance studies revealed that metal-ion-intercalated bimetallic MXenes exhibit excellent electrocatalytic hydrogen evolution performance and good stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of transition metal ion modified bimetallic MXene, in particular to modifying bimetallic MXene with transition metal salt solution to improve its surface chemical properties and electrochemical performance, which is widely used in energy storage, catalytic reaction, supercapacitor and other fields. BACKGROUND

[0002] MXene is a kind of two-dimensional material composed of transition metal carbide, nitride or carbonitride, which is usually obtained from layered precursors by chemical etching method. This material has excellent electrical conductivity, high specific surface area, adjustable surface chemical properties and strong mechanical strength, so it has wide application in the fields of energy storage, catalysis, sensors and supercapacitors. However, although MXene material itself has good electrochemical performance and catalytic activity, its electrical conductivity, stability and catalytic activity in practical application still need to be further improved.

[0003] In recent years, researchers have proposed surface modification of MXene by metal ion intercalation strategy to improve its electrochemical performance and catalytic activity. Metal ion intercalation can introduce transition metal ions (such as Ni 2+ , Co 2+ , Cu 2+ , etc.) into the interlayer of MXene, adjust its surface charge density and electronic structure, and thus improve its interaction with electrolyte, enhance its electrical conductivity and catalytic performance. For example, the intercalation of nickel, cobalt and other transition metal ions not only improves the electrical conductivity of MXene, but also improves its performance in battery, supercapacitor and other electrochemical devices.

[0004] Bimetallic MXene, as a new modified form of MXene material, can realize the synergistic enhancement of material performance by introducing two different transition metal elements (such as Ni and Co, Ni and Cu, etc.). Bimetallic MXene not only has more abundant structure and surface chemical properties than single metal MXene, but also provides more active sites and higher electrochemical activity, which makes it have more extensive application prospect in the fields of electrochemical energy storage and catalytic reaction.

[0005] Although previous studies have shown that metal ion intercalation can effectively modify MXene, the existing technology mainly focuses on the influence of metal ion intercalation on single metal MXene, and the modification effect of transition metal ion intercalation on double metal MXene has not been fully studied. In particular, how to realize efficient modification of double metal MXene by adjusting the type and concentration of metal salt has not been effectively solved. Therefore, how to optimize the intercalation process of metal ions to adjust the surface chemical properties and electrochemical performance of double metal MXene is an important challenge in the current technical field.

[0006] The present application provides a method for efficiently modifying double metal MXene by adjusting the type, concentration and intercalation conditions of metal salt solution to optimize its performance, especially in electrochemical energy storage and catalytic applications. SUMMARY

[0007] The present application provides a method for preparing transition metal ion modified double metal MXene, which aims to control the type and concentration of metal salt to adjust the surface chemical properties and electrochemical performance of double metal MXene, thereby improving its application effect in energy storage and catalytic reaction. The method of the present application comprises reacting MXene material with a transition metal salt solution, and the transition metal ion forms a stable chemical bond with the surface of the MXene material through ion exchange or intercalation, thereby improving the surface conductivity, stability and catalytic activity of the MXene. The method is simple to operate, has strong adaptability, and can optimize the performance of the MXene without changing its basic structure.

[0008] Through the preparation method of the present application, the obtained transition metal modified double metal MXene exhibits significantly improved electrochemical performance, such as high specific capacity, excellent electrical conductivity, high catalytic activity, etc., and is particularly suitable for supercapacitors, batteries, catalysts, etc.

[0009] The technical scheme of the present application is as follows: a transition metal ion modified double metal MXene as a HER electrode material, which is prepared by intercalating transition metal ions into layered double metal MXene.

[0010] A method for preparing transition metal ion modified double metal MXene, comprising the following steps:

[0011] (1) Mo2TiAlC2 powder is added to a concentrated HCl mixed solution containing NaF, and stirring is performed for etching reaction. After etching is completed, centrifugation, washing and vacuum drying are performed to obtain Mo2TiC2T x ;

[0012] In some embodiments, in step (1), the product is washed with DI water several times by centrifugation during the washing process until the pH of the supernatant is greater than or equal to 6, such as 6-7.5.

[0013] (2) Mo2TiC2T x is dispersed in a glass bottle containing water, degassed by argon gas, and then sealed for ultrasonic exfoliation at room temperature to obtain monolayer Mo2TiC2T x ;

[0014] In some embodiments, in step (2), the water is DI water, and the ultrasonic exfoliation time is not less than 8 h, generally 8-12 h.

[0015] (3) The monolayer Mo2TiC2T x is dispersed in a glass bottle containing water, a solution of a transition metal salt of appropriate concentration is added, and an inert protective gas is introduced, then sealed and stirred to perform intercalation reaction, obtaining intercalated sample Mo2TiC2T x -M.

[0016] (4) The intercalated sample Mo2TiC2T x -T is centrifuged, washed, and vacuum dried to obtain a transition metal ion modified bimetallic MXene product.

[0017] In step (1), the concentration of NaF is 0.3-1 g / mL, and the mass concentration of concentrated HCl is 36-38%.

[0018] In step (1), the etching reaction temperature is 70 ± 5 ℃, and the etching reaction time is 2-7 days.

[0019] In step (3), the concentration of Mo2TiC2T x dispersion is 0.5-5 mg mL -1 .

[0020] In some embodiments, the optimal concentration of Mo2TiC2T x dispersion is 1 mg mL -1 .

[0021] In step (3), the transition metal salt is any one of acetate, nitrate, sulfate, halide salt of nickel, cobalt, manganese, iron, and copper; and the concentration of the transition metal salt solution is 0.1-1 mM.

[0022] In some embodiments, the optimal metal salt is nickel acetate (Ni(OAc)2); and the optimal concentration of nickel acetate (Ni(OAc)2) in step (3) is 1 mM.

[0023] The adding speed of the transition metal salt solution in step (3) is controlled at 0.5-1 mL / min.

[0024] The inert gas in step (3) is argon and nitrogen; the flow rate of the inert protective gas is 20-50 mL / min.

[0025] The intercalation reaction temperature in step (3) is 40-80℃, the intercalation reaction time is 8-48 h, and the intercalation reaction stirring speed is 200-800 rpm.

[0026] In some embodiments, the optimal intercalation temperature is 60℃, the optimal intercalation time is 24 h, and the optimal stirring speed is 500 rpm.

[0027] The prepared transition metal ion modified bimetallic MXene has a sheet structure, the interlayer spacing is increased, and the transition metal intercalation makes the material edge present an irregular shape, thereby providing more active sites for the material.

[0028] Another technical solution of the application is the application of a transition metal ion modified bimetallic MXene in electrocatalytic hydrogen evolution (HER).

[0029] The transition metal ion intercalated Mo2TiC2T x After the material is subjected to basic characterization, the electrocatalytic hydrogen evolution performance of the material is tested, and the specific method is as follows:

[0030] Mo2TiC2T x -M is prepared into a uniform electrode dispersion liquid and is drop-coated on a carbon cloth, and after drying, a catalytic working electrode is successfully prepared, and the loading amount of the catalyst is 0.5 mg cm -2 -Ag / AgCl electrode is used as a reference electrode, a platinum wire is used as a counter electrode, and 0.5 M H2SO4 is used as an electrolyte, in order to exclude the influence of Pt on the hydrogen evolution reaction, an H-type electrolytic cell is used for electrochemical test. x -1 mM Ni 2+ exhibits excellent electrocatalytic hydrogen evolution performance and has super-long stability.

[0031] The application has the following beneficial effects:

[0032] (1) The synthesis method is simple and efficient: the application adopts a metal ion intercalation strategy, and through liquid phase etching and subsequent intercalation reaction, the preparation of Mo2TiC2T x -M material is successfully realized. The synthesis process is simple and easy to operate, and has low requirements on equipment, and is suitable for large-scale production.

[0033] (2) Optimized structure design: the intercalated metal ions (such as Ni 2+ , Co 2+, Mn 2+ significantly expands the interlayer spacing of Mo2TiC2T x , forming a loose lamellar structure. This structure increases the specific surface area of the material, providing more active sites for electrocatalytic reactions, while enhancing the contact efficiency with the electrolyte.

[0034] (3) Enhancing electronic structure and conductivity: Metal ion intercalation optimizes the electronic structure of the material, promoting the redistribution of interface charges, significantly reducing the charge transfer resistance (Rct), and improving the charge transport rate, providing kinetic advantages for the electrocatalytic hydrogen evolution reaction (HER).

[0035] (4) Excellent catalytic performance: Benefiting from the structural optimization and electronic regulation of metal ion intercalation, Mo2TiC2T x -Ni 2+ requires only 93 mV overpotential at a current density of 10 mA cm⁻², with a Tafel slope of 80 mV·dec -1 , significantly better than non-intercalated materials and other metal intercalated samples (such as Co 2+ and Mn 2+ ).

[0036] (5) Excellent long-term stability: After 700 hours of long-term stability test at a current density of 10 mA cm -2 , Mo2TiC2T x -Ni 2+ catalyst still maintains good structure and electrocatalytic performance, with voltage fluctuation only within 100 mV, showing excellent cycle stability.

[0037] (6) Wide application potential: The metal ion intercalation strategy of the invention is applicable to the performance optimization of other MXene materials, not only showing excellent performance in hydrogen evolution reaction (HER), but also widely applicable to other electrocatalytic reactions and energy storage fields. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 XRD diagram of Mo2TiC2T + intercalated with different concentrations of Ni x synthesized in Example 1.

[0039] Figure 2 Scanning electron microscope image of Mo2TiC2T x -Ni 2+ synthesized in Example 1.

[0040] Figure 3 Transmission electron microscope image of Mo2TiC2T x -Ni 2+ synthesized in Example 1.

[0041] Figure 4 Mo2TiC2T synthesized for Example 1 Example 2 Example 3 x LSV plot for M.

[0042] Figure 5 Concentration of Ni synthesized for Example 1 + Intercalated Mo2TiC2T x LSV plot for M. DETAILED DESCRIPTION

[0043] The present application is further illustrated by the following examples, but the scope of the present application is not limited to the scope of the examples.

[0044] Monolayer Mo2TiC2T x Preparation of M.

[0045] (1) 0.5 g of Mo2TiAlC2 powder was slowly added to a mixed solution of concentrated HC1 (36-38%) containing NaF (0.5 g / mL), followed by stirring at a certain temperature for several days. After etching was completed, the product was washed several times with DI water by centrifugation until the pH of the supernatant was 6.5. Finally, the obtained black sample was vacuum dried for several hours, and Mo2TiC2T x was finally collected.

[0046] (2) An appropriate amount of etched Mo2TiC2T x sample was dispersed in a glass bottle containing DI water, and was continuously purged with argon gas for degassing treatment, and was sealed for ultrasonic exfoliation at room temperature for 8 h to obtain monolayer Mo2TiC2T x .

[0047] Example 1 (1 mM Ni 2+ intercalation, Mo2TiC2T x -Ni 2+ Preparation of M.

[0048] 20 mg of monolayer Mo2TiC2T x was dispersed into 20 mL of 1 mM nickel acetate (Ni(OAc)2) solution, and was continuously purged with inert protective gas argon for 15 min, and the glass bottle was sealed and stirred at 60°C at a rate of 500 rpm for 24 h to obtain intercalated sample Mo2TiC2T x -Ni 2+ . The intercalated powder sample was collected by centrifugation at 5000 rpm, and was washed several times with deionized water to obtain Mo2TiC2T x -Ni 2+ sample. Mo2TiC2T x-Ni 2+ At 10 mA cm -2 The overpotential at the current density is 92 mV.

[0049] XRD shows different concentrations of Ni 2+ Insertion of Mo2TiC2T x The expansion of interlayer spacing had no significant effect. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that after metal ion intercalation, Mo2TiC2T… x -Ni 2+ The microstructure underwent significant changes. Figure 3 SEM images show that after intercalation, Mo2TiC2T x The tightly layered structure becomes loose, forming a sheet-like structure, and the interlayer spacing increases. Figure 4 TEM analysis further validated this result, Mo2TiC2T x The original layered structure was destroyed, and the overall morphology became more porous. Meanwhile, Ni... 2+ Intercalation creates irregular shapes at the material edges, providing more active sites. Figure 5 The LSV curves of different transition metal salt ions show that Ni 2+ Intercalated Mo2TiC2T x - Ni 2+ It has the lowest HER overpotential (92 mV).

[0050] Example 2 (1 mM Co) 2+ Intercalation, Mo2TiC2T x -Co 2+ (Preparation)

[0051] By replacing the aforementioned transition metal salt with cobalt acetate (Co(OAc)2), and using the same experimental conditions as in Example 1, Mo2TiC2T can be obtained. x -Co 2+ Mo2TiC2T x -Co 2+ At 10 mA cm -2 The overpotential at the current density is 282 mV.

[0052] Example 3 (1 mM Mn) 2+ Intercalation, Mo2TiC2T x -Mn 2+ (Preparation)

[0053] By replacing the aforementioned transition metal salt with cobalt acetate (Mn(OAc)2), and using the same experimental conditions as in Example 1, Mo2TiC2T can be obtained. x -Mn 2+ Mo2TiC2Tx - Mn 2+ The overpotential at 10 mA cm-2was 186 mV. -2 The overpotential at 10 mA cm-2was 186 mV.

[0054] Example 4 (0.1 mM Ni 2+ intercalation, Mo2TiC2T x - Ni 2+ )

[0055] The concentration of the above nickel acetate (Ni(OAc)2) dispersion solution was changed to 0.1 mM, and other experimental conditions were the same as in Experimental Example 1, to obtain Mo2TiC2T x - Ni 2+ . Mo2TiC2T x - 0.1 mM Ni 2+ The overpotential at 10 mA cm-2was 165 mV. -2 The overpotential at 10 mA cm-2was 165 mV.

[0056] Example 5 (10 mM Ni 2+ intercalation, Mo2TiC2T x - Ni 2+ )

[0057] The concentration of the above nickel acetate (Ni(OAc)2) dispersion solution was changed to 10 mM, and other experimental conditions were the same as in Experimental Example 1, to obtain Mo2TiC2T x - Ni 2+ . Mo2TiC2T x - 10 mM Ni 2+ The overpotential at 10 mA cm-2was 170 mV. -2 The overpotential at 10 mA cm-2was 170 mV.

[0058] Example 6 (NaF etching Mo2TiC2T x )

[0059] 0.5 g of Mo2TiAlC2powder was slowly added to a concentrated HC1 (36-38%) mixed solution containing NaF (0.5 g / ml), and then stirred at a certain temperature for several days. After etching was completed, the product was washed several times with DI water by centrifugation until the pH of the supernatant was 6.5. Finally, the obtained black sample was vacuum dried for several hours, and Mo2TiC2T x was finally collected. An appropriate amount of the etched Mo2TiC2T x sample was dispersed in a glass bottle containing DI water, and continuously purged with argon for degassing treatment, and sealed for ultrasonic exfoliation at room temperature for more than 8 h to obtain monolayer Mo2TiC2T x . Mo2TiC2T xThe overpotential at 10 mA cm -2 The overpotential at 10 mA cm

[0060] Example 7 (LiF etching Mo2TiC2T x )

[0061] The 0.5 g Mo2TiAlC2 powder was slowly added to a concentrated HCl (36-38%) mixed solution containing LiF, with a LiF concentration of 0.5 g / ml, and then stirred at a certain temperature for several days. After etching was completed, the product was washed several times with DI water by centrifugation until the supernatant pH was 6.5. Finally, the obtained black sample was vacuum dried for several hours, and the Mo2TiC2T x was finally collected. An appropriate amount of etched Mo2TiC2T x sample was weighed and dispersed in a glass bottle containing DI water, and argon was continuously introduced for degassing treatment, and sealed for ultrasonic exfoliation at room temperature for more than 8 h to obtain single-layer Mo2TiC2T x . The Mo2TiC2T x etched by LiF has an overpotential of 410 mV at 10 mA cm -2 .

[0062] The present application designs and synthesizes a series of Mo2TiC2Tx-M electrocatalysts by a simple and mild metal ion intercalation method. The metal ions are uniformly distributed in the interlayer and surface of Mo2TiC2T x MXene, significantly improving its electrocatalytic hydrogen evolution performance in acidic electrolyte. Metal ion intercalation effectively expands the interlayer spacing of MXene, making its layered structure more loose and presenting a flaky morphology, which is conducive to increasing the contact area of the catalyst and the electrolyte and providing more reaction active sites. In addition, the metal ions can be stably anchored on the Mo2TiC2T x MXene, forming a strong metal bond and promoting efficient electron transfer, thereby improving the catalytic performance. By adjusting the type and concentration of metal ions, the hydrogen evolution activity and stability of the catalyst are further optimized. This interlayer space adjustment strategy provides a new idea and possibility for the application of MXenes in the field of electrocatalysis.

[0063] The above examples are only preferred technical solutions of the present application, and should not be regarded as limiting the present application. The examples in the present application and the features in the examples can be combined with each other as long as they do not conflict. The protection scope of the present application should be based on the technical solutions recited in the claims, including equivalent replacement solutions of the technical features recited in the claims. That is, within this scope, equivalent replacement improvements are also within the protection scope of the present application.

Claims

1. A method for preparing transition metal ion-modified double metal MXene, characterized in that, The synthetic method comprises the following steps: (1) Mo2TiAlC2 powder is added into a concentrated HCl mixed solution containing NaF, and etching reaction is carried out by stirring, after etching, centrifugation, washing, and vacuum drying, Mo2TiC2T x is obtained. (2) Mo2TiC2T x was dispersed in a glass bottle with water, degassed by argon, and sealed at room temperature for ultrasonic exfoliation to obtain single-layer Mo2TiC2T x ; (3) dispersing the single-layer Mo2TiC2T x in a glass bottle containing 0.1-1 mM transition metal salt solution, passing in inert protective gas, sealing and stirring to carry out intercalation reaction, the Mo2TiC2T x dispersion has a concentration of 0.5-5 mg mL -1 , the transition metal salt is any one of acetate, nitrate, sulfate, halide of nickel; the intercalation reaction temperature is 40-80℃, the intercalation reaction time is 8-48 h, to obtain the intercalation sample Mo2TiC2T x -Ni 2+ ; (4) The intercalation sample Mo2TiC2T x -Ni 2+ The transition metal ion modified double metal MXene product was obtained by centrifugation, washing, and vacuum drying.

2. The method of claim 1, wherein the transition metal ion-modified double-metal MXene is prepared by the steps of: The concentration of NaF in step (1) is 0.3-1 g / mL; the mass concentration of concentrated HCl is 36-38%.

3. The method of claim 1, wherein the transition metal ion-modified double-metal MXene is prepared by the steps of: The etching reaction temperature in step (1) is 70 ± 5 ℃, and the etching reaction time is 2-7 days.

4. The method of claim 1, wherein the transition metal ion-modified double-metal MXene is prepared by the steps of: The adding speed of the transition metal salt solution in step (3) is controlled at 0.5-1 mL / min. 5.The method of claim 1, wherein the transition metal ion-modified double-metal MXene is prepared by the method comprising: preparing a transition metal ion-modified double-metal MXene by mixing a transition metal ion solution and a double-metal MXene solution. The inert gas in step (3) is argon and nitrogen; the flow rate of the inert protective gas is 20-50 mL / min.

6. The method of claim 1, wherein the transition metal ion-modified double-metal MXene is prepared by the steps of: The stirring speed of the intercalation reaction in step (3) is 200-800 rpm.

7. The method of claim 1-6, wherein the transition metal ion-modified double metal MXene is prepared by the method comprising: preparing a transition metal ion-modified double metal MXene by mixing a transition metal ion solution and a double metal MXene solution. The prepared transition metal ion modified double-metal MXene has a sheet structure, the interlayer spacing is increased, and the transition metal intercalation makes the edges of the material present irregular morphology, thereby providing more active sites for the material.

8. Application of the transition metal ion modified double-metal MXene prepared by the method in any one of claims 1-7 as an electrocatalytic material for hydrogen evolution.

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